A440 Explained: Why Is 440 Hz the Standard Tuning Pitch?

What concert pitch is

Before you can tune anything, everyone has to agree on how high one note is. That agreed note is called the reference pitch or concert pitch, and by convention it’s the A above middle C, written A4. Hertz (Hz) counts vibrations per second, so A4 = 440 Hz means that note vibrates 440 times every second.

Once A4 is fixed, every other note follows by math. The A an octave up (A5) is exactly double, 880 Hz. The A an octave down (A3) is half, 220 Hz. The notes in between divide each octave into twelve equal steps. That’s why changing the reference on a tuner also changes the target for, say, a guitar’s low E string: move A4 from 440 to 442 and every note rises by the same small ratio.

How 440 Hz became the standard

For most of music history there was no single standard. Pitch varied from city to city and orchestra to orchestra, and over time it tended to creep upward. Higher pitch made music sound brighter, but it was hard on singers, and that pushed people to agree on a fixed value.

• France, 1859. A law set A at 435 Hz. This “diapason normal” spread beyond France for a while.
• London, 1939. An international conference recommended A4 = 440 Hz.
• ISO. The International Organization for Standardization adopted the 440 Hz value. Today the standard ISO 16 sets A4 = 440 Hz as the standard tuning frequency.

That’s why almost every tuner, digital keyboard and recording app defaults to 440 Hz. The tuner on this site starts at 440 Hz too.

Who tunes higher (or lower)

A standard doesn’t mean everyone uses it.

• Slightly higher. Some ensembles tune a little above 440. Wikipedia’s “A440” article notes that in continental Europe, A4 commonly varies between 440 and 444 Hz. Some orchestras and choirs use 442 Hz; Leonard Bernstein, for example, often tuned the New York Philharmonic to A442. It differs by group and even by concert, so “orchestras tune to 442” isn’t a rule you can rely on. Ask, or measure.
• Lower, for early music. Ensembles playing Baroque music on period instruments often use around 415 Hz, roughly a semitone below 440. Historical pitch actually varied a lot from place to place, so 415 is best understood as a modern convention among period-instrument players.

If you practice alone, a difference of a hertz or two hardly matters. When people play together, though, even small differences show up as a wobbling, beating sound. What matters most is that everyone in the room uses the same reference.

Tuning before a rehearsal

Orchestras traditionally tune to an A played by the oboe. All the string instruments have an open A string, and the oboe’s bright, focused tone carries well across the stage. When a piano is part of the group, everyone tunes to the piano instead, since its pitch can’t be adjusted on the spot.

For a small group or band, this routine works well:

1. Agree on a reference before you start. Without a specific reason, use 440 Hz.
2. If there’s a piano or keyboard, measure its A with a tuner and have everyone match that value.
3. Set every tuner to the same reference, then tune.
4. Strings drift, so check again between songs.

Changing the reference on a tuner

In our tuner, open Reference A4 in the settings and choose anything from 430 to 450 Hz in 1 Hz steps. Your choice is remembered next time you open the tuner, and it applies to every instrument page, including the violin tuner.

A few tips:

• If you’re not playing with anyone, leave it at 440 Hz.
• Playing along with a recording or backing track? Measure the track’s A with the tuner and match it.
• Playing with other people? Double-check that everyone is using the same number.

About 432 Hz

You’ll find plenty of claims online that tuning to 432 Hz sounds more “natural” or is good for your body or mind. 432 Hz is about 32 cents lower than 440 Hz, roughly a third of a semitone. The LaRouche movement’s Schiller Institute promoted it under the name “Verdi tuning,” without much success.

Claims that it has healing properties, however, are regarded as specious: they sound plausible but aren’t backed by evidence. Whether 432 Hz simply sounds better to you is a matter of taste. If you’re curious, set the tuner to 432 Hz, tune up and compare for yourself. Just remember that when you play with other people or with a recording, everyone needs to be on the same reference.